In this tutorial, YouTuber Hiroyuki Narisawa explains how to use Astro Focus Lock, a new feature in the Tamron Lens Utility™ app. Designed with astrophotographers in mind, this tool helps achieve precise, consistent focus on stars and other celestial subjects in your night sky photography. He will also provide solutions for common issues encountered in astrophotography.
By Hiroyuki Narisawa
What You’ll Learn in This Article:
- How to use Astro Focus Lock for fast and accurate star focusing
- Tips to avoid common astrophotography focusing errors
- Adjusting to shifting environmental conditions like humidity and temperature
- How to fine-tune infinity focus without touching your lens
- Recommended Tamron lenses for night sky photography
The three principles of photography are 1) focus, 2) exposure, and 3) composition. If you nail 1 and 2, you can produce something that will be accepted as a photograph. But in the astrophotography genre — the photography of night skies – nailing those two principles can be decidedly tricky, and many photographers have issues trying to solve them.
Achieving sharp focus can be influenced by factors like lens performance, focal length, and shooting conditions. As a YouTuber, I’ve had many people come to me for advice on their astrophotography focusing challenges. While I’ve tried to help, I haven’t yet found a perfect solution that works for everyone.
That was until TAMRON introduced a feature that might just be the answer to all those troubles. I’m talking about the new Astro Focus Lock (Astro FC-L), available through the TAMRON Lens Utility™ .
Preparation for Astrophotography
The method for achieving proper focus in astrophotography is to enlarge a bright light source—such as a star or streetlight—and use manual focusing to make that light source appear as small as possible.
That’s easy to describe on paper, but in practice, it can be quite difficult. Even in total darkness, it’s often hard to make things out on an LCD monitor. Photographers’ eyesight can vary, and focus can also be influenced by air temperature and humidity.
Many photographers have likely experienced getting the focus just right at the beginning of a shoot, only to continue shooting for an extended period—then later discover, after checking their photos at home, that many shots were out of focus. Achieving sharp focus becomes even more challenging when using standard or telephoto lenses instead of wide-angle ones.
Sometimes, touching the focus ring causes camera shake, making it hard to lock onto a light source. Other times, there simply may not be any bright stars in the area you want to photograph, leaving you without a clear reference point for focusing.
Enter the Astro Focus Lock Feature on the TAMRON Lens Utility™ App
An effective way to address these challenges is Astro Focus Lock (Astro FC-L), the new feature offered through the TAMRON Lens Utility™. Lenses are designed with a specific infinity focus point, known as the optical infinity focus.
Astro FC-L can be used with TAMRON lenses equipped with a USB-C port. By connecting the lens to a computer or Android smartphone, the app automatically recognizes the lens and, with a single tap, focuses it to its optical infinity focus point.
The feature is simple and intuitive. With the mobile version, just connect the lens to an Android device using a USB cable and tap [Astro FC-L]. The lens will instantly adjust to the optical infinity focus point.
After that, all that’s left is to set your exposure and press the shutter. The first time I used this feature, I was genuinely surprised by how convenient and effortless it was.
Use the Astro Focus Lock Without a Smartphone
If your lens is equipped with a Focus Set Button, you can set it to activate the [Astro FC-L]. This means that even without the Android smartphone, you can direct your lens to focus to its optical infinity focus point.
Fine-Tune Focus in the Field Without Ever Touching the Lens
I refer to optical infinity as the designed infinity focus point because, in reality, the position of infinity can shift depending on the shooting environment. Modern lenses incorporate vibration compensation and autofocus mechanisms, involving movement of internal elements. When air temperature drops or humidity rises, these elements can shift based on the materials or optical design—altering the focus point.
In fact, I’ve experienced a situation where a lens did not focus to true optical infinity at 1 °C (33.8 °F). Fortunately, Astro Focus Lock allows for easy fine-tuning even under such conditions. Once you disengage Astro FC-L, the focus can be further adjusted through the app.
As shown in the image below, the left side of the on-screen focus ring is for major adjustments, while the right side handles fine adjustments. Pinching the fine adjustment area enlarges the image, allowing for even more precise control. Being able to adjust focus without touching the lens—especially when shooting outdoors—feels truly revolutionary.
In astrophotography, we sometimes use soft filters to give stars a more glamorous appearance by making them look larger and more diffused. This effect, too, can be influenced by air temperature and humidity.
During one session at 6 °C (42.8 °F), I was still able to adjust the focus to optical infinity without any issues. However, as noted earlier, the focal point can shift depending on environmental conditions. That’s why I strongly recommend checking focus regularly throughout your shoot to ensure your images remain sharp.
With a simple tap, you can instantly set focus on the night sky—and keep it there. Even with a lens heater attached, you can make focus adjustments without ever touching the lens’s focus ring.
After Trying Out the New Astro Focus Lock in TAMRON Lens Utility
Focus adjustment in astrophotography has long been a challenge for many photographers who admire capturing the night skies. I believe TAMRON’s Astro Focus Lock (Astro FC-L) feature in the Lens Utility will go a long way in helping solve that issue. I encourage everyone to take advantage of this revolutionary new focusing tool and embrace the challenge of photographing the stars.
Astrophotography Time-Lapse Video Using the Astro Focus Lock [Astro FC-L] Featured in the TAMRON Lens Utility
Learn More About the TAMRON Lens Utility
TAMRON Lens Utility is dedicated software that can customize functions and update the firmware of TAMRON lenses equipped with a Connector Port (USB Type-C) using a computer or a smartphone. Personalizing lens settings to match your shooting style allows you to be more creative and makes photography more fun.
See more about the 4.0 Version>
Hiroyuki Narisawa’s Favorite Tamron Lenses for Astrophotography
- Tamron 20-40mm F/2.8 Di III VXD: Lightweight ultra-wide to standard zoom, ideal for capturing expansive night sky scenes with fast aperture and compact design.
- Tamron 28-75mm F/2.8 Di III VXD G2: Versatile and sharp, perfect for more detailed compositions of the Milky Way and night landscapes.
- Tamron 35-150mm F/2-2.8 Di III VXD: A premium zoom with exceptional image quality, great for deep-sky astrophotography with precise framing options.
Final Thoughts
Whether you’re just beginning your journey into night sky photography or you’re a seasoned astrophotographer looking to streamline your workflow, Tamron’s Astro Focus Lock offers a simple yet powerful solution to one of the genre’s most persistent challenges—achieving reliable, precise focus in ever-changing conditions.
Combined with the intuitive TAMRON Lens Utility™ and a lineup of high-performance Tamron lenses, this feature helps you spend less time worrying about focus and more time capturing the awe-inspiring beauty of the cosmos. Give it a try and elevate your astrophotography experience.
Learn more about Tamron lenses at an authorized Tamron dealer near you or visit the TAMRON Store.
About Hiroyuki Narisawa
Born May 31, 1980. From Rumoi, Hokkaido. Currently living in Saitama Prefecture. Night sky photographer, time-lapse creator, and YouTuber. Full member of the Japan Professional Photographers Society (JPS). Fujifilm Academy X instructor, Nikon NPS member. Holds numerous night sky photography seminars at camera specialty stores and mass retailers across the country. Serialized articles in camera magazines and web magazines. Shoots general astronomical sky photography (night sky and celestial bodies) and time-lapse of a wide range of subjects. He is particularly skilled at expressing the time-lapse of sunsets, stars, and sunrises, known as the “Holy Grail”. After working at a photo studio and a telescope manufacturer, he became independent in April 2020. He began his activities as a YouTuber in earnest to hone his video shooting and editing skills. He strives to disseminate a variety of information. Website | YouTube
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